Selection of techniques to detect and map subsurface organic contamination depends on the type of source, contamination, and hydrogeologic setting. Ideally, an investigator, manager, or enforcement official could choose mapping techniques such as soil gas and geophysical measurements, coring, or installing wells to delineate the contamination in a sequence of progressively greater precision and expense. This paper presents the results of applying several of the above techniques to a service station with a leak from a gasoline storage tank. The merits of and information gained from geophysical and soil gas measurements are compared to the results from analysis of water samples at existing wells.